If you want to carry out repairs on or re-cover less than 25 per cent of the area of a pitch or flat roof, you will not normally need to submit a building regulations application. You will need approval, however, if:
1. You carry out structural alterations
2. The performance of the new covering will be significantly different to that of the existing covering in the event of a fire
3. You are replacing/ repairing more than 25 per cent of the roof area, in which case, the roof thermal insulation would normally have to be improved.
There are separate rules for construction of new roofs.